Unlike traditional drugmakers, compounders don’t need FDA approval for their versions of drugs on the market

A new kind of drugmaker is emerging to meet demand for lower-priced medicines by custom-making drugs, sparking pushback from federal health regulators and legal challenges from traditional pharmaceutical companies.

These companies are marketing cheaper versions of brand-name drugs but they differ from traditional generic-drug makers because they operate much like pharmacies that mix their own medicines, though often in larger quantities. That allows them to skip the regulatory approval process through which traditional drugmakers...